Corruption needs to stay and that corruption affecting prodution is called waste. We still have both today in the real world. There should be both at the beginning of the game and courthouses should fix some of it, but then later in the game, techs should reduce it more. Techs that help with waste would be Engineering, Motorized Transportation, Computers and Robotics. Techs that would help with corruption would be Printing Press, Nationalism, Radio and Computers.
Pollution also needs to stay. It isn't hard to clean up or keep track of at all. By the time pollution starts to show up, I have most of my terrain improved and my workers are automated using Shift-A. They wion't mess with my improvements but when that pesky pollution shows up, they are on it immediately, without me having to worry about them missing some.
As for MPP being replaced by NAP, thats what an ROP is already. ROP means you don't attack that civs units that venture into your territory and they won't attack yours. NAP is the same exact thing. What MPP should be changed to is Alliance. It was nice being able to help defend your ally's troops and cities by puting your units into the same squre as theirs. Yuo should, however, have the option to not declare war on your mutual enemy. It would of course hurt relationships but you should have the option to back out. Italy did that in WWI. They were allied with Germany and Austria-Hungary and actually joined the other side.
Changes I would like to see would be:
1. Birng back the Alliance, as I said above.
2. Change the way units work. Instead of making a unit and it goes out on its own, you have to form it into a group. By that I mean, you make one unit. You can immeiately form that unit into a squad or you can wait until you have a second unit and form them into a platoon. Then when battles occur, instead of it being my one dinky little Knight attacking your one dinky little Pikeman, its my army made up with Pikeman, Longbowmen and Knights attacking your defending army made up of the same units. Then you get to see an animation of the two armies advancing on eachother if it is out in the open, or one army advancing on the city and the other army defending. Now I'm probably just dreaming and most civ fans will hate this idea but it was still fun to tell it.
3. Make it so you have to leave jungles and forests on the map. Yoiu can still clear some, but if you clear too many, global warming occurs.
4. Trades being broken and its not your fault, but you get the blame.
5. Put in an option to request a civ to end its war with another civ, like in SMAC.
6. Improve naval warfare.
There are probably some more changes I would like to see but I can't think of them right now.
